1. Field of the Invention
The present invention relates generally to magnetic loop antennas, and more particularly to the integration of loop antennas at or within a wearer's clothing.
2. Description of the Related Art
Magnetic loop antennas have a number of applications, including incorporation as part of transmitting systems, and are particularly applicable to methods of communication underwater using electromagnetic and/or magneto-inductive means. Because water, especially seawater, is partially conductive, relatively low signal frequencies are commonly employed in communication systems underwater in order to reduce signal attenuation. To this end, antennas in many applications are generally formed of conducting loops.
Such magnetic loops generate an alternating magnetic field whose strength is commonly defined by the well-understood term, magnetic moment. For signal detection at greatest distance, the largest achievable magnetic moment is desirable. The magnetic moment is directly proportional to each of the three parameters: loop area, loop current, and number of loop turns. Equivalently, it may be stated that the magnetic moment is proportional to both the ampere-turn product of the loop and to the enclosed area of the loop.
The number of loop turns and current are restricted in practice by the driving circuit and the available power supply. It is beneficial to maximise the area enclosed by the loop but a physically large structure will severely impede a wearer's movement. This limitation has been one of the factors restricting the adoption of low frequency radio communications by wearers.